


just your bff's brother

by aubadezayn



Series: TUMBLR PROMPTS [5]
Category: Supernatural
Genre: Alternate Universe - College/University, Bisexual Dean, Dean/Cas BFF, First Dates, First Kiss, Getting Together, Little Bro!Sam, M/M, Mechanic Dean, Starbucks, Student Castiel, Student Sam, TA!cas
Language: English
Status: Completed
Published: 2015-08-31
Updated: 2015-08-31
Packaged: 2018-04-18 07:22:28
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,855
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4697249
Author URL: https://archiveofourown.org/users/aubadezayn/pseuds/aubadezayn
Summary: <blockquote class="userstuff">
              <p><a href="http://willingwinchester.tumblr.com">willingwinchester</a>, the sam to my cas, requested: “Maybe a sastiel fic where cas and dean are best friends and sam is in love with his brother’s best friend?”</p>
            </blockquote>





	just your bff's brother

**Author's Note:**

> HEY CHECK ME OUT ON TUMBLR: [CASTIELADRIFT](http://castieladrift.tumblr.com)

For as long as Sam can remember, Dean and Cas have been inseparable. 

When he was just a toddler, they were learning to ride a bike together. They were having their “first day of school” photos taken together, they watched cartoons together every Saturday. His brother would camp out in the backyard with Cas, and they wouldn’t let him in the tent because he was just a baby. 

“One day, baby, you’ll be older and then you can play with Dean and Cas too.” His Mom had comforted him every time, his tiny toddler hands wrung up in her dress as she sewed Dean and Cas’s torn jeans from roughhousing.  He’d dreamt of the day when he could be like the big boys, when he could go down to the river with his big brother and Cas. 

But he was always behind a few years. When he was in 5th grade, Dean and Cas were entering 9th. And when he was finally in 9th, they were seniors working on college applications and going to prom and parties, and Sam was still the baby. 

This, though. This was finally his time. 

College. Freshman year at Kansas State, and though Cas was a senior Sam knew it wasn’t like in high school. When Cas seen Sam on campus, or they hung out between classes, there wasn’t a polite smile for him being Dean’s younger brother. Their conversations didn’t revolve around what Dean and Cas were doing, though they were still very sturdily best friends.  

When Sam bought Cas coffee and flirted shamelessly, the look in his eyes was much less “you’re my best friend’s sweet baby brother, you’re Dean’s Sam” and much more “you’re a man, you could be  _my_  Sam.”

Of course though, there was the little problem of Dean. It didn’t really feel right to make a serious move on Cas without at least talking to Dean first. What if Dean got pissed at him? Or what if Dean wanted Cas for himself? Who knows?

Dean had come out as bisexual in his junior year and Mom’s exact response had been,  _“Oh good, honey. You get that from your Father, now do you want meatloaf or a casserole for dinner?”_

So, all this had lead up to Sam standing outside the garage where Dean worked, staring up at the sign and wringing his hands nervously. He would have liked to stand out there for at least another hour, going back and forth with himself, but someone must have noticed the 6 foot tall man standing outside and told Dean. 

“Hey, Sammy!” Dean shouted, coming outside in his greasy coveralls, wiping his hands off on a rag. “What’s up? Why you here?" 

"Uh just wanted to visit you at work, how’s it goin? I also got you lunch.” Best way to butter Dean up was to literally get him some butter, so Sam had driven the 40 minutes to Dean’s favorite diner and gotten the greasiest Cajun fries and burger from Benny. His hand shook a little bit as he handed him the styrofoam box but Dean didn’t notice.

“Oh shit, awesome man I’m starvin’.” Dean sat down on the bench in front of the garage, and Sam  collapsed next to him, his knees feeling weak. “Okay so, you drove all the way to Benny’s to get this for me, what do you want?” Dean took a huge bite of burger, smearing barbecue sauce all over his face like an animal. Sam had a hard time imagining Cas kissing that, and while he was thinking of Cas kissing anyone, his mind kind of fried itself and his mouth kept going.

“Cas. I want Cas.”

Dean froze, his burger halfway up to his mouth. His face was stuck mid-chew and surprised, which was kind of gross to look at honestly. “Uh,” Dean looked away putting his burger down. “Alright, so like…you want Cas? To do what?”

“Date me, I guess.” Sam continued, looking away at the road next to the garage. There was a dead raccoon across the way and Sam empathized with it. 

“Oh.” Dean didn’t say anything else, and Sam wasn’t sure if he should continue. “You and Cas, huh?” Dean didn’t seem mad, at least, just stunned.

“Yeah uh, we’ve been hanging out and talking a lot. You know he’s my TA for sociology so I see him all the time.” They both lapsed into silence, that was somewhere between awkward and peaceful. Dean shoved a couple fries into his mouth and the only sound was his chewing. 

“You didn’t need my permission, Sam. Cas is my best friend, that’s it. ” Finally, seeming to overcome the shock Dean smiled, and held out a fry. “Go for it, bro. Get the guy.”

—–

With Dean’s blessing, Sam found that dating Cas became an even more daunting task. Wanting to date him was simple chemistry; oxytocin building up in Sam’s brain every time he sees Cas smile or hears Cas moan around hot coffee in the cold mornings before sociology. Sure he wants to date Cas, sure he thinks they’d be great together, but he’s also been idolizing Cas since he was like 3 and that’s a pretty daunting challenge.

It’s about five AM the Monday after his talk with Dean when Sam finally pulls himself out of bed. He doesn’t have classes for a couple more hours, and usually he wouldn’t get up for at least another hour and a half, but he’d never went to sleep. He’d tried, and slept fitfully for a while before waking up and staring at the ceiling all night. He had to do it today, no matter what, before Dean and Cas met up and Dean spilled the beans for him.

He took a shower, washing his hair and blow drying it afterwards. He could practically hear Dean’s mocking voice saying he was primping for Cas. Which he was, honestly. He spent too much time getting his hair just right and too little time watching the clock, and ended up being dressed and ready barely an hour before class. 

“Hey, Sam!” Charlie, a computer programming major that lived across from his apartment, called. “Where you goin’ in such a hurry?”

“Gotta get Cas his coffee, sorry! I’ll talk to you later!” Sam shouted back, already hurrying down the several flights of stairs between their apartment. Charlie came over to the banister, holding a Rubix cube mug and smiled down at him. 

“Today the big day?” She grinned, laughter in her voice. 

He didn’t have the time to be surprised she knew so he just paused  and smiled back up at her. “Yep, wish me luck?”

“Go forth and get the princess, Mario.”

—

Starbucks is packed as usual, and the entire time Sam’s in line, he’s bouncing anxiously from foot to foot. He needs to get to Cas before class starts, because Cas leaves for his internship right afterwards. Sam won’t be able to see him till way later, and by then Dean could have already spoken to him. 

“Dude, could you calm down? You’re making me anxious.” He stops bouncing immediately and looks down at the pint-size girl glaring up at him. She’s gotta be like fifteen and wearing too much black, and her t-shirt has a dude on it that looks a lot like him strangely enough.

“Sorry,” He apologizes, her glare making him sweat. She rolls her eyes and the glare falls back.

“What is it? You gotta pee or somethin’?” It’s probably not appropriate to ask a stranger that but Sam’s too keyed up to mind. He shakes his head and winces.  
“I’m just late for something important." 

"I’m already way late for school.” She shrugged, stepping forward one spot in the line. “You can get in front of me, if you want.” She moved back to let him in front, and checking his watch, he slid in front of her. 

“You should be at school, school’s important.”

“Yeah, thanks Grandpa. So is it your girlfriend you’re late for?” She pried as they inched forward in line. 

“Uh, no, not my girlfriend.” Sam shyly answered. 

“Your boyfriend?”

Sam blushes and shrugs. "Almost.” 

“Good luck,” She smiled. “You’re next.”

Sam turned to see the flustered barista waiting on him, and he quickly stepped up to the counter. “Hi, can I get a veinte pumpkin spice latte with non fat milk? Actually just make that two.” He could use a healthy dose of sugar. 

He handed the barista his card and stepped away to the side as the girl who’d let him skip her ordered a veinte caramel frappucino. She came over a minute later and he smiled, opening his mouth to tease. “You know-”

“It’s a milkshake,” She cut him off smiling, “I know, and I’m fifteen and can still drink them.”

“Pumpkin spice for Sam!” The barista dropped the drinks on the counter and disappeared back into the fray. Sam gathered them both up and smiled. The girl smiled back and gave him two thumbs up.

“Good luck, Sam.”

——

Sam made it onto campus with twenty minutes to spare. He would have liked to have been there a little earlier so he could catch Cas outside, instead of inside where everyone could watch him make a fool of himself, but he rushed inside anyway.

The lecture hall was mostly empty with a few people scattered through the seats, but Cas was down below behind the teacher’s desk shuffling papers and preparing for the day. Sam trotted down the steps smiling nervously. “Hey, Cas.”

He extended the coffee and Cas smiled widely. “Thank you, Sam. My morning just got a lot better.” He took a sip of the coffee, foam lingering on his lips. 

Sam coughed awkwardly and tried to judge if his smile was getting too big for normal conversation. “Cause of the coffee? Glad to be of help.”

“Also because of you.” Cas whispered conspiratorially, his voice dropping to a tone that made Sam’s knees shake. The look in Cas’ eyes now was what had started it all, that acknowledgement that Sam wasn’t a kid anymore and neither was Cas.

“Really?” Sam asked quietly, legs shaky. 

“Of course.” They seemed to gravitate towards each other, Cas leaning against the desk and Sam leaning into Cas. Thankfully the students in the room were absorbed in finishing the reading or texting their friends and didn’t care about the TA. They were quiet for awhile, just staring into each other, Cas’ hands wrapped tightly around his latte. 

Sam’s smile never seemed to lessen.

“Do you want to get dinner with me?” Sam blurted out.

“Come over tonight.” Cas blurted out at the exact same time. His cheeks reddened and he looked down at his coffee before looking back up at Sam from under his eyelashes. “I can make dinner.”

“ _We_  can make dinner.” Sam reiterated, his smile so big it hurt. He leaned in near Cas’ ear and whispered, “Afterwards  _we_  can do some other things too.”

Then he kissed Cas’ cheek, the stubble rough against his lips. Finally his knees didn’t shake.

Finally he got his guy.

**Author's Note:**

> COMMENTS MUCH APPRECIATED, THANKS FOR READING!


End file.
